Television scanning system



Jamo 27, 1931. T. A. SMITH TELEVISION SCANNING SYSTEM Filed Aprili, 19292 sheets-sheet 1 ra rece/vs@ f A` SMITH ips 5mm@ 3 mi- 2751931. r. A.sMm-l f TELEVISION scAHNING SYSTEM Filec April 1, 1929 2 Sheets-Sheet` 2SMT/OMAR Y ,4l/16901? INVENTOR TA BY() ATTORNEY atented Jan. 27, 1931UNITED "STATES PATENT OFFICE THEoDoRE A. SMITH, oF RInGEwoo-D, NEW'.JERsEY,Ass1GNoR "ro Ramo CORPORA- 'rIoN oF AMERIQA, A CORPORATIONOFDELAWARE TELEVISION SGANNING- SYSTEM The present invention relates totelevision systems, and, particularly, to a methodand means by Whichthetelevision subject may rality of built-up horizontal or verticallines.-`

be scanned or analyzed and then reproduced on aV screen or the like.

It has heretofore been the custom intelevision systems of the type mostcommon, such as in the rotating disk or mirror disk, or-

drum scanning and reproducing systems, to scan the field by means of anumber of successive parallel lines formed from a series of points oflight traced across the field. Such scanning action breaks the pictureor subject to be transmitted or reproduced into a number of divisions,usually horizontal, although a vertical division is also of the samegeneral type. With this typeoi system a spot of`light is caused tomovehorizontally or vertically across the field or subject from one' edge tothe other, and then to move once more across the field or subject' alonga: parallel line adjustedto but lower than or to the right orv left fromthe previous line. This action is then repeated untilthe complete fieldor subject has been scanned or analyzed by a plu# Such action isrepeated at a rate of at least .16 times per second in order that thecomplete subject may be scanned at a rate corresponding to thepersistency of vision of the human eye vso as to produce the effect ofan -optical illusion in which the 'entire picture appears `to besimultaneously projected .upon the screen, although, in reality,successive points and lines are projected, but

each'point or line is repeated at a rate'corl responding to thepersistency'of vision.

With a system of the above described type objection has been found inthe fact that in the case of horizontalscanning any diagonal linesappearing in the subject are reproduced as stepped lines, and curvedlines are reproduced at the receiver as a jagged line of the averagecurvature of the original line. Another objection resides in the factthat although the received picture may be transmitted and reproduced inits entirety by a rate greater than the repetition necessary to producethe optical illusion of a continuous ly moving picture, or, at a rate atleast equal the fact that the picture has tothe persistency of vision,Aa pronounced flicker appears. This is apparently due to n,ot been pro.jected upon the screen in its entlretybut was built up of successiveelements, and, because picture is being scanned and reproduced,the humaneye fails to retain the image of the lower portion of the picture andthis latter portion, therefore, appears dark. This dark v band at theopposite portion of the picture from that which is being scanned appearsto travel up and down or across the screen, and thus causes an annoyingflicker when a person-views the received image.

vention,`I have sought to develop a method and means for substantiallyeliminating the4 undesirable flicker from received television images. 4if y A.

Asa `further object of my invention, I have sought to 'develop 'a methodand means by which a television subject may be scanned or analyzed, andthen reproduced in a sequential manner along paths bearing an angularrelationship to each other so asto reduce flicker to asubstantialdegree. y l

' 'Still a urtherobject of 'my invention vis to provide a methodandmeans by which a` television Subj ect may be scanned and thenreproduced so that diagonal or curved lines in the original subject maybe free from any substantial distortion and .will not appear as steppedlines.

Still other objects of my invention are' to produce a method and meansfor scanning and reproducing television subjects which is simple in itsconstruction and arrangement of parts, a system which is easilyoperated, readily installed, conveniently set up, substantiallyfoolproof in its operation, and eiicient in its use.

Still other and ancillary objects of my invention will at once becomeapparent and suggest themselves to those skilled in the art maticallyand conventionally represent a 100 .55 of the fact that While the upperpart of the i Therefore', as a principal object of this in- ,to whichthe invention has'been drected'by system for either scanning oireproducing a television subject according to my novel method ofscanning and reproducing along different paths in a sequential manner.

y the accompanying drawings, Fig. 1 represents a suitable means forscanning in a vertical direction, and Fig. 2 represents a suitable meansfor scanning in an angular direction to that shown by Fig. 1, or alonglines in a horizontal direction.

Fig. 3 shows the system of Figs. 1 and 2 combined into a single figure,wherein for the position shown the light from the source will be causedto trace a vertical path upon the picture screen, while for thehorizontal path which will be traced upon further rotation of thescanning element, the assumed path is shown by dotted lines. Fig. 4graphically represents the relationship between the series of linesproduced by each of the fixed reflecting ,systems cooperating with therotatable scanning element.

More particularly, my invention has been directed to a system 'in whichthe scanning action takes place in a sequential manner hy alternatingbetween horizontal and vertical lines of scanning so that the successivelines by which the picture is analyzed will be at right angles to eachother. although it is to he recognized that where desired, and withoutdeparting from the basic principles of my invention, the angle whichsuccessive scanning actions bear to each other may vary within widedegrees, and may be at any angle suitably chosen.

Thus, to describe, for purpose, of illustration, the system as one inwhich the picture is'lirst analyzed along horizontal lines, then alongvertical lines, and then analyzed again and again by repeating thisprocess, the human eye is unable to distinguish the particular directionof reproducing each of the separate pictures on account of theirrapidity, and the resultant picture appears as a combinationl of the twodistinct types of scanning motion. The produced picture may appear to bebroken up into small squares in- 'stead of lines, but the divisionbetween squares will be much dimmer than those between the lines, andtherefore less objectionable; and further, the stepped effect issubstantially reduced because of the fact that it is entirely differentfor the two types of scanning, and the combination of the two types ofscanning neutralizes the distortions in each direction and the combinedpicture appears more natural than that produced along either of thecomponent lines of scanning. Further than this, it is possible to'reduce the flicker to a material extent hecause of the changing indirection of the moving band and because of the 4kfact that the flickerfrequency would be substantially changed.

To refer now more particularly to the ac- "mirrors forming the portion 5of the drum are so tilted and stepped that .they reflect light beamsdownwardly from the disk or drum along adjacent parallel paths.

The drum disk 1 may be mounted in any convenient manner upon a spindle7, for eX- ample, and rotated from any-desired type of prime mover (notshown), for example, a synchronous motor wh'ose rotation is controlledby incoming television signals of the general type described and claimedin my copending application, Serial ift-322,704, filed November 30,1928, and driven in the direction indicated by the arrow appearing onthe drum disk.

' As shown, the arrangement has been particularly directed to atelevision reproducing system, wherein, incoming television signals varearranged to illuminate 4the glow lamp 9 so as to produce a glow therein.The light from the lamp 9 is then directed by means of a lens system 11so as to project itself as a point source on the drum disk 1 at a point1 3, for example, as shown. It is preferable, although not essential, toprovide a glow lamp in which the illumination therefrom is as a pointsource so that it may be more readily focused as a point source upon theindividual mirrors forming the series 3 or 5 of the drum disk 1. As thedrum disk 1 is rotated in the direction shown by the arrow, the point oflight focused thereon by means ofthe lenssystem 11 is caused to travelacross the-mirror, and thus, due to the change in angular position ofeach adjacent mirror, the light beam from the glow lamp o'r otherappropriate source is reflected along different paths.

As shown particularly in connection with Fig. 1 of the drawings, thelight beams issuing from the glow lamp source 9 have been shown asdirected against the set of mirrors 3 so as to be reflected in an upwarddirection from the disk 1 so as to travel along a path 15, for example,where they will impinge upon a stationary mirror 17 and trace pathsthereacross in a direction indicated by the arrow. From the mirrors 17,the light is again reflected along a path generally designated as 19,and is projected upon a second stationary mirror 21 from which it isrellected along a path 23, for example, so as to trace lines in avertical direction upon the screen 25 in a direction thereacross shownby the arrow, so that over half of a revolution v of the disk 1, acompletel picture of the teleby the arrow.

vision subject is built up upon the screen 25 in a vertical manner, sothat consecutive lines of reproduction are parallel to 'each other andextend across the screen 25 in the direc# tionvshown by the single line27' indicating the'manner in-which the picture is lbuiltup.

N ow referring more particularly to Fig. 2, after the disk or d rum 1has turned through a half revolution .so as to bring the light beamsissuing from the glow lamp 9 upon the set of mirrors 5, the lightbeams-are reflected from the mirror surface of the disk 1 along a pathgenerallydesignated as 29' to a stationary mirror 31A arranged below thedrum disk 1. The stationary mirror 31 is .tilted at an appropriate angleso that light beams reflected therefrom along a path 33, for example,will trace horizontal paths 35 across the screen 25 in the direction asshown It is thus seen' thatthe 'stationary mirrors 17, 2 1 and 31 mustbe fixed andappropriately located so that the an le of tilting thereofis such that all light refected from the mirror surfaces composinggroups of mirrors 3 and5 upon the drum 1 will'eventually-be projected asa point lsource upon the screen 25. Thus, as the drum 1 is rotated, thelines by which the picture is reproduced will sequentially oralternately and successively be composed of groups of horizontallyextending lines due to the reflection of the group of mirrors 5, andvertically extending parallel lines due to the reflection of the groupof mirrors 3 upon the drum disk 1.

Afterthe picture is horizontally scanned or reproduced the verticalscanning and re production is repeated. A f

As has been shown, the drum disk 1 is composed of two distinct sets ofmirrors, 3 and 5, and each of these sets of mirrors may preferably be ofsuch a number that the complete picture will be reproduced therefrom,and' supposing, for example, that a fifty line picture were' to bedesired, the' drum 1 should carry about its periphery one hundreddistinct mirror surfaces. This-number of mirrors would be-divided intotwo groups, 3 and 5, wherein, the fifty mirrors of group 3 should'all bearranged to reflect light in an upward direction, for example, from thedisk, and the fifty mirrors of group 5 should be arranged to reflectlight in a downward direction from the drum. It is thus apparent that byutilizing a scheme of the type herein described, it is possible also toreduce the speed of rotation of the disk member by fifty percent,although due to the increase in the number of mirrors about theperiphery of the disk, the peripheral speed of the disk must beincreased over that of a disk having a smaller number of mirrors.

According to the above description, the system has been describedVseparately as to the vertical and horizontal scanning as producedrespectively by the arrangements of Figs.` l and 2, but it should beunderstood lvthat both of. the arrangements of Figs.1 and 2are-operating in a sequential manner, and the 'system as a whole hasfurther been schematically-shown by-Fig. 3, wherein the con- -trolledlight source is in the position of the disk shown adapted to produce avertical line upon thescreen, whereas, upon further rotation of thedisk, so thatthe light from' the source 9'reaches the mirror surface 5,horizontal'lines will be produced upon the screen, as shown by thedotted line paths 29 and 33, which are respectively directed andreflected 'to and from the stationary mirror surface 31.

The vertical and horizontal vpaths of reproduction are Aconventionallyillustrated by Fig..4, wherein thelines 27, 27show the vertical scanningpaths, while the lines35, 35

show the horizontal scanning paths which occur after the picture hasbeen rebuilt completely along vertical paths, and-then continue untilthe picture has been reproduced completely along horizontal paths., atwhich time the verticalscanning is repeated. Y

It will also be apparent that a scheme of the type herein described mayalso be readily applied to a lens disk or drum without materiallychanging theconstruction and arrangement of parts, and I, therefore,desire to make all such modifications and changes as may readily suggestthemselves to those skilled in the art to which the invention re-Vlates, provided, of course, such modifications and changes fall fairlywithin the spirit and scope-of the invention as defined in thehereinafter appended claims.

Having now described my invention, what .Y

I claim and desire to secure Y by Letters Patent is the following:

- 1. In a television system, a mirror disk and;

associated reflector system cooperating with one portion of the saidmirror disk for scan ning and reproducing a television subjectV along aparallel set direction across the subject, a second reflector systemcooperating with the second portion of said mirror disk for scanningandreproducing the same subject along a second set of parallel linesextending at an angular direction to said first named .set of scanningand reproducing lines, and means operable upon each half revolution ofsaid disk for cyclically changing. from one to the other of said sets ofscanning' and reproducing lines ata rate commensurate with thepersistency of vision.

of lines extending in one 2, In a television system, a screen for re-Aproducing a television subject, a rotary scanningelement and a reflectorsystem cooperating with a portion thereof for illuminating said screenalong series of parallel. aths eX- tending transverse thereto, a seconreflector system cooperating with the second portion of said rotaryscanning element for illuminating said screen at a later period of timealong a set of parallel lines extending longitudinally thereof, andmeans dependent upon the rate of revolution of said rotary scanningelement for alternately and successively changing from one to the otherof said paths of illumination at a rate equal to that necessary toeffectively maintain the impression that all of said lines are beingcontinuously illuminated.

3. In a television system, a scanning and reproducingr disk, a pluralityof sets of fixed reflecting bodies associated with said disk, a lightsourcejor projecting light upon said disk, and means provided by saiddisk for tracing on said reflecting bodies a plurality of parallel pathsof an intensity corresponding to the intensity of light and shadow on apicture subj ect, and means provided by said disk for cyclicallyshifting the said parallelly projected lines of lillumination from oneto the other of said reflecting bodies at periods when light valuescorresponding to the entire television subject have been projected uponeach of said mirrors.

4. In a television system, a scanning and reproducing disk, a pluralityof sets of oppositely tilted mirrors about the periphery thereof, saidmirrors being arranged in sets for alternately and successivelyprojecting light impinging thereon in an upward and downward directionfrom the plane of said disk, whereby light impinging upon said disk maybe caused to trace a pair of paths each composed of a group ofparallelly extending lines extending at an angular direction withrespect to each other.

5. In a television system, a scanninv and reproducing disk, a pluralityof sets oiJ mirrors arranged about the periphery of said disk, one ofsaid sets of mirrors being arranged to deliect light impinging thereonalong a set of parallel lines upwardly from the plane of said disk, andthe other of said sets of mirrors being arranged to project lightdownwardly from the plane of said disk along a setof parallellyextending lines, a mirror surface positioned above said disk along thepath of reected light beams therefrom, a screen, means associated withsaid mirror for tracing paths of illumination upon said screen in adirection extending vertical thereof, a mirror arranged beneath saiddisk for tracing paths of illumina-tion upon said screen in a.horizontal direction, and means for rotating said disk and changing fromone toanother of said paths at a rate commensurate with the persistencyof vision.

G. A television system for scanning and reproducing television subjectsincluding a light source, a rotating disk arranged in the path ofsaidlight, a plurality of sets of mirrors arrangedabout the periphery ofsaid disk, one of said sets of mirrors being arranged to continuouslyproject the light imarranged to pro] disk for cyclically 'pinging uponthe periphery thereof alonga set of parallel lines in a plane above saiddisk, and the other of said sets of mirrors -ect the light impingingthereon along a set of parallel lines in a plane beneath said disk, ascreen for reproducing a television image, a mirror positioned beneathsaid disk for reiecting the light projected thereon from said disk as aplurality ot' sets of parallel lines and tracing the same across saidscreen as a set of parallel lines horizontally thereof, a mirrorpositioned above said disk for reflecting the light beams projected asparallel paths of light upwardly from said disk, and a second diagonallypositioned mirror associated with said last named mirror for tracing thelight beams projected upwardly' from said disk as a set of parallellyextending. lines vertically uponl said screen, and means provided by therotation of said changing from one to the other of said sets of parallellines of reproduction at a rate commensurate with the persiste'ncy ofvision.

7. ln a television system, a screen for reproducing a television image,a scanning and reproducing disk, a light source for projecting lightupon said disk, a plurality of sets of mirrors arranged about theperiphery ot' said disk, one of said sets of mirrors being arranged todeflect light impinging thereon along a set of parallel lines upwardlyfrom the plane of said disk, and the other of said sets of mirrors beingarranged to project light downwardly from the plane of said disk along aset of parallelly extending lines, a mirror surfacepositioned above saiddisk along the path of reflected light beams therefrom, means associatedwith said mirror for tracing parallel paths of light upon said screen ina direction extending vertical thereof, a mirror arranged beneath saiddisk for ltracing parallel paths of light upon said screen in ahorizontal direction, and means Jfor rotating said disk and changingfrom one to another of said paths at a rate commensurate with thepersistency of vision.

8. A. system for scanning and reproducing television subjects includinga source of illamination, a rotating disk arranged in the path of saidillumination,'a plurality of sets of mirrors arranged about theperiphery of said disk, one of said sets of mirrors being arranged tocontinuously project the light ilnpinging thereupon along a set ofparallel lines upwardly from said disk, and the other of said sets ofmirrors arranged to project the light impinging thereon along a set ofparallel lines downwardly from said disk, a screen for reproducing atelevision image, means positioned beneath said disk for reiecting thelight projected in one direction from said disk and cause said light tofocus on said screen to' trace a set of parallelly extending lineshorizontally of said screen,

means positioned above said disk for rellecting the light beamsprojected in a second direction from said disk and cause said light to.focus on said screen to trace a set of parallelly extending linesvertically upon' said screen, and means provided by the rotation of saiddisk for cyclically changing from one to the other of said sets ofparallel lines at a rateV commensurate with the lperistency of vision.9. In a television system, a rotary scanning and reproducing element anda plurality of V sets of reilecting systems cooperating there'- with forcausing diierent portions of said rotary scanning element to trace lightpaths bearing Van angular relationship to each other.

10.",In'a television system, a scanning and reproducing elementrhaving aset of upwardly tilted mirrors and a set of downwardly y zoftilt'edmirrors about the periphery thereof for projecting light impingingthereon in an upward and downward directionfrom the plane of said disk,and a plurality of fixed reliecting systems cooperating therewithwhereby'light impinging upon said disk may be caused to tracealternately a pair of paths each composed of'a group of parallellyextending lines each extending at an angular direction with respect toeach other.

THEODORE 'A. SMITH.

